
lol, I thought you wanted the 1st scenario to be a huge map with accurate starts for all civs so that peeps could become familiar with the mod itself. My bad, thouroughly misunderstood you. Ok, I'll put this map on hold then.
If your talking a civil war scenario, that cuts the US map roughly in half. I suppose you could use the western half of the map as supply lines from the major cities of that era, then use the Natives to harass the established rail roads. But in a straight up Civil war scenario, it's primarily going to be the eastern part of the map.
Additionally, your only going to be using a limited amount of the flavor civs of this mod. Not to mention the amount of work that needs to be done for city placement, units, military leaders, etc. This would basically be a modmod all in it's own Keldath, IMO it would be better to focus on the heart of this mod first, create a couple of custom scenarios (maybe call them fractured America or something) using the civs inherent in this mod, and then see what we can do to further it's creation. Just some thoughts, and all concerned voice their input as well please.
1) Arrival and Survival (vs NA and other euro trash

)
2) The 13 States ( let's kick King George in the codpiece People)
3) The Great land Rush ( Chisholm, John Chisholm, weary and saddle sore! <John Wayne reference

>)
4) Like the Abolitionism
5) Manifest Destiny (screw the Supreme Court, It's our land and the Natives are restless anyway)
6) Industrial revolution ( Mwahahaha! greed is good, so screw the little guy)
7) War and Progress ( so the tea lovers need help vs the Kaiser? sure, why not)
8) War and Progress part Deux ( really? again? wait a sec, ya got something on your lip, I'll fix it)
9) Like the Progressive.
10) World Stage ( let's announce our power with authority!)
11) Superpower ( wonder twin powers- activate)
12) Infinity and Beyond ( moon, schmoon, It's Alpha Centauri or bust Mister!)
Lol, Sorry. Was having a bit of fun at your list.
Tech Tree; As I recommended earlier, Take base BTS, add the uniquely American techs, then toss in some foofy stuff from Europe/Asia. This will simulate the American tech progress fairly accurately.
ColRev scenario; I really think Civ Col assets are portable to BTS, so that could help out a lot in that regards for a scenario. All that we would have to do is tailor the specifics and add whatever details that would be necessary to accomplish this.
As always, these are just my thoughts. You obviously have a pre-defined goal in mind, so that makes giving input for you a little difficult

. If you could perhaps be a little more concise on what your vision is, I might be able to assist (or others as well) you better.